OB.H

The public symbol file NTKRPAMP.PDB for the original release of Windows 10 tells that the kernel is built with the OB.H header at

d:\th\minkernel\ntos\inc

and draws from it the following type definitions:

Line Number Type NTOSP.H NTOSIFS.H
147 struct _OBJECT_DUMP_CONTROL 43868 1402
157 enum _OB_OPEN_REASON 43878 1412
303 struct _OBJECT_TYPE_INITIALIZER 44024 1488
347 struct _OBJECT_TYPE 44068  
381 struct _OBJECT_DIRECTORY 44097  
393 struct _OBJECT_DIRECTORY_ENTRY    
404 struct _OBJECT_SYMBOLIC_LINK    
422 struct _OBP_SILODRIVERSTATE    
437 struct _OBJECT_HANDLE_COUNT_ENTRY    
446 struct _OBJECT_HANDLE_COUNT_DATABASE    
479 struct _OBJECT_CREATE_INFORMATION    
494 struct _OBJECT_HEADER 44111  
556 struct _OBJECT_HEADER_PADDING_INFO    
560 struct _OBJECT_HEADER_AUDIT_INFO    
565 struct _OBJECT_HEADER_QUOTA_INFO    
575 struct _OBJECT_HEADER_HANDLE_INFO    
582 struct _OBJECT_HEADER_PROCESS_INFO    
592 struct _OBJECT_HEADER_NAME_INFO 44171  
623 struct _OBJECT_HEADER_CREATOR_INFO    
634 struct _OB_HANDLE_REVOCATION_BLOCK    
1110 struct _OB_DUPLICATE_STATE    

The header OB.H is not known in any Device Driver Kit (DDK) or Windows Driver Kit (WDK).